1. Field of the Invention
This invention relates to a combination gas cleanup process for the removal of sulfur dioxide and nitrogen oxides from a gaseous mixture.
2. Description of the Prior Art
Processes for the removal of sulfur dioxide or nitrogen oxides from gaseous mixtures are known.
It is known to use cerium oxide for the removal of sulfur oxides from flue gases at a temperature of 500.degree. to 600.degree. C. and to regenerate the cerium oxide by utilizing a reducing gas. See U.S. Pat. No. 4,001,375 which is hereby incorporated by reference.
U.S. Pat. No. 3,885,019 discloses a process for removing oxides of nitrogen in an exhaust gas utilizing a catalyst of cerium oxide in the presence of ammonia at a temperature ranging from 200.degree. to 650.degree. C. In specific examples, temperatures above 500.degree. C. are disclosed.
U.S. Pat. No. 4,115,516 discloses the use of cerium oxide or cerium sulfate as the starting reagent for the removal of nitrogen oxides in the presence of ammonia (see col. 2, lines 30-35 and col. 1, lines 53-68).
It has now been found that sulfur dioxide and a nitrogen oxide can be removed from a gaseous mixture containing both of these undesired components at the same temperature when certain cerium compounds are utilized.